Smelt (Osmerus mordax) Mortality

Observation by Lindsey Markoff:

Thousands of smelts found dead during low tide in the Togiak slough. This is significant to the community of Togiak because it impacts the subsistence way of life questioning if the smelts are unsafe to eat also very unusual seeing many dead, wondering what is the cause to this devastating impact about the smelt fish, one of many food sources during the winter months.

Tom Okey, from Ocean Integrity Research, writes:

There are very strange things happening ecologically in the Bering Sea due to this extremely warm water and lack of ice. The ice and the ice edge are important for the production and distribution of food. One thing we know happens with a lack of ice and much warmer water is changes in primary and secondary production, and this can translate into less food for smelt and many other marine organisms. Of course, other factors influencing smelt mortality can be acting in concert with such food stress, such as changes in pathogens, and of course toxicity of particular plankton that thrives in warmer temperatures or is otherwise benefited by warmer seas. To determine if the fish suffered from food stress (or related pathogens), observers could assess the body condition of the smelt. If they do this, it would be best if they could evaluate a large number of smelt for body condition. There are methods for doing this, but in the case of this community, it might be even more valuable for them to devise a qualitative body condition scale, such as with five points, 5 being the healthiest (e.g. fattest).

Ted Meyers, State Fish Pathologist with the Alaska Department of Fish and Game, writes:

In our experience mass fish mortality is generally related to unfavorable environmental conditions rather than infectious disease ranging from: 1) pollution (either chemical or sewage) in more urban areas from runoff or industrial effluent that either kill fish directly or indirectly deplete the oxygen; 2) algal blooms in warmer waters that may be toxic or deplete the oxygen and may damage gills; 3) in northern latitudes, where pollution is less common, die-offs have been related to weather and climate changes that increase water temperatures (such as the blob this past summer) that send forage bases, such as plankton or small fish, elsewhere, often resulting in starvation of resident fish or birds dependent on that food source. Also, 4) other unfavorable weather conditions such as wind combined with tides can blow fish off course causing stranding at low tides and 5) temporary barriers (ice, shifting sand, etc) that entrap fish, again at the low tidal cycle.

The photographs show little detail of individual fish to determine whether they appear normal or not. In the future, the photographs should include close-ups of individual fish to observe for potential abnormalities, if any.

Comments from LEO Editors:

This observation has been forwarded to the Togiak National Wildlife Refuge